When I read your post I can imagine how sad and difficult this was for your friend, and what she had to go through. I went to a similar situation on my first marriage and belive the least thing one wants to do is call the police for a lot of reasons. Embarrasment, fear that he takes revenge or his own family preassuring one not to press charges.
It's good to know that she had you by her side as a support, I got to a point that I got tired of the situation and called the police myself and proceed to move on with my lfe and children. I hope that your friend found the courage to better her life and children. Good post!